Empirical evidence and conceptual elaboration reveal and rationalise the remarkable affinity of organic ionic liquids for biomembranes. Cations of the so-called room-temperature ionic liquids (RTILs), in particular, are readily absorbed into the lipid fraction of biomembranes, causing a variety of observable biological effects, including generic cytotoxicity, broad anti-bacterial potential, and anti-cancer activity. Chemical-physics analysis of model systems made of phospholipid bilayers, RTIL ions and water confirm and partly explain this evidence, quantifying the mild destabilising effect of RTILs on structural, dynamical and thermodynamic properties of lipids in biomembranes. Our Feature Article presents a brief introduction to these systems and to their role in biophysics and in biotechnology, summarising recent experimental and computational results on their properties. More importantly, it highlights the many developments in pharmacology, bio-medicine and bio-nano technology expected from the current research effort on this topic. To anticipate future developments we speculate on: (i) potential applications of (magnetic) RTILs to affect and control the rheology of cells and biological tissues, of great relevance for diagnostics; and on: (ii) the usage of RTILs to improve the durability, reliability and output of bio-mimetic photovoltaic devices.

The thermodynamics, structures, and applications of thermoresponsive systems, consisting primarily of water solutions of organic salts, are reviewed. The focus is on organic salts of low melting temperatures, belonging to the ionic liquid (IL) family. The thermo-responsiveness is represented by a temperature driven transition between a homogeneous liquid state and a biphasic state, comprising an IL-rich phase and a solvent-rich phase, divided by a relatively sharp interface. Demixing occurs either with decreasing temperatures, developing from an upper critical solution temperature (UCST), or, less often, with increasing temperatures, arising from a lower critical solution temperature (LCST). In the former case, the enthalpy and entropy of mixing are both positive, and enthalpy prevails at low T. In the latter case, the enthalpy and entropy of mixing are both negative, and entropy drives the demixing with increasing T. Experiments and computer simulations highlight the contiguity of these phase separations with the nanoscale inhomogeneity (nanostructuring), displayed by several ILs and IL solutions. Current applications in extraction, separation, and catalysis are briefly reviewed. Moreover, future applications in forward osmosis desalination, low-enthalpy thermal storage, and water harvesting from the atmosphere are discussed in more detail.

We propose a spatially and temporally nonlocal exchange correlation (XC) kernel for the spin-unpolarized fluid phase of ground-state jellium for use in time-dependent density functional and linear response calculations. The kernel is constructed to satisfy known properties of the exact XC kernel to accurately describe the correlation energies of bulk jellium and to satisfy frequency-moment sum rules at a wide range of bulk jellium densities, including those low densities that display strong correlation and symmetry breaking. These effects are easier to understand in the simple jellium model than in real systems. All exact constraints satisfied by the recent MCP07 kernel [A. Ruzsinszky et al., Phys. Rev. B 101, 245135 (2020)] are maintained in the revised MCP07 (rMCP07) kernel, while others are added. The revision $f_{\mathrm{XC}}^{\text{rMCP07}}(q,\omega )$ differs from MCP07 only for nonzero frequencies $\omega$. Only at densities much lower than those of real bulk metals is the frequency dependence of the kernel important for the correlation energy of jellium. As the wave vector $q$ tends to zero, the kernel has a $-4\pi \alpha \left(\omega \right)/q^2$ divergence whose frequency-dependent ultranonlocality coefficient $\alpha \left(\omega \right)$ vanishes in jellium, and is predicted by rMCP07 to be extremely small for the real metals Al and Na.

Computer simulations show how nano-structural motifs in organic salts/water solutions change with salt content increasing from dilute to highly concentrated.

Structural and magnetic properties of thin Mn films on the Fe(001) surface have been investigated by a combination of photoelectron spectroscopy and computer simulation in the temperature range $300\mathrm{K}<~T<~750\mathrm{K}.$ Room-temperature as deposited Mn overlayers are found to be ferromagnetic up to 2.5-monolayer (ML) coverage, with a magnetic moment parallel to that of the iron substrate. The Mn atomic moment decreases with increasing coverage, and thicker samples (4-ML and 4.5-ML coverage) are antiferromagnetic. Photoemission measurements performed while the system temperature is rising at constant rate $(dT/dt\sim 0.5\mathrm{K}/\mathrm{s})$ detect the first signs of Mn-Fe interdiffusion at $T=450\mathrm{}\mathrm{K},$ and reveal a broad temperature range $(610\mathrm{}\mathrm{K}<~T<~680\mathrm{K})$ in which the interface appears to be stable. Interdiffusion resumes at $T>~680\mathrm{K}.$ Molecular dynamics and Monte Carlo simulations allow us to attribute the stability plateau at $610\mathrm{K}<~T<~680\mathrm{K}$ to the formation of a single-layer MnFe surface alloy with a $2\times 2$ unit cell and a checkerboard distribution of Mn and Fe atoms. X-ray-absorption spectroscopy and analysis of the dichroic signal show that the alloy has a ferromagnetic spin structure, collinear with that of the substrate. The magnetic moments of Mn and Fe atoms in the alloy are estimated to be $0.8{\mu }_B$ and $1.1{\mu }_B,$ respectively.